Another New Forge

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Greetings Folks! I'm still a little new around here, but after tons of reading, this seems like the place to be! And for that I say thank you! I've been doing a little casting work with a waste oil burner furnace I built a couple of years ago. However, I've grown tired of sticking long rods down into the furnace and getting burnt in the process when I need to bend metal.... So it's time to build a forge. I'm using a shortened portable air tank lined with Kaowool and coated with Mizzou and it MUST be fueled by natural gas. I'm in a residential area so of course the NG pressure will be low. I've got the ribbon burner built from Mizzou and have been working on a 2inch mixing pipe for the forced air and gas feed. At the moment, I'm introducing the natural gas about 20 inches from the burner to allow for a good mix. (I think) I already have the John Emmerling pdf and the Wayne Cohen pdf as well. (big help) I'm surprised I haven't found much here on what I'm doing. I've searched and searched but all I find are threads without endings and threads with missing photos. :-(

I'm kinda looking for some ideas on the fuel nozzle. Is one even necessary? My main gas supply is 1/2" black pipe, but I was going to try just 1/4" for starters and see if that's enough when I force air at it. I haven't nailed down a blower yet as I have several laying around to choose from. Some are squirrel cage fan designs and others are fan blade based. SO I guess I've got some experimenting to do on that one. WC suggestions would be helpful here. Anyhow, here's where I'm at for now, been busy with other things, so I'm just plugging away on this thing.

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Nice build Jason I can see you've done this before. By "this" I'm referring to following plans and even merging different ones without hopelessly confusing yourself.

Nothing special needed for a gas "nozzle" just an open end near the center is fine. You put two hard turns in the mixing tube, that'll do it. The plenum in the ribbon burner is a final mixing chamber as well as equalizing the air fuel supply to the final nozzles.

I like an impeller blower over a squirrel cage or shudder fan. When I make a gun burner using an impeller blower I feed the fuel into the blower air intakes and let the impeller do the mixing. This eliminates the need for hard bends in the mixing tube, frankly eliminates the need for a mixing tube.

Normally I'm a naturally aspirated burner guy but have made, tuned and used guns a few times. So that's just my opinion I'm sure there are better set ups.

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1/4" should be way more than enough but it's better to have it and not need it than need it and not have it. A LITTLE larger than you need is okay you can turn it down but you can't turn one up higher than max if it's not enough. 1/8" is probably enough in reality.

I'm not a gun burner guy, I'm sure there are guys here with a lot more experience making the things than I have.

I've never used a squirrel cage so I don't know if one develops enough pressure to make a ribbon burner work. I pick up mattress, raft, etc. inflator blowers at yard, garage, etc. sales. The 12v ones make excellent field expedient forge blowers plugged into the cigarette lighter a little pipe and you're good to go. There are also 120v inflate alls that do the same job on house current. These things will inflate a 6 man raft in pretty short order and they develop decent pressure I'm sure they'll make a ribbon burner work.

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You've got a nice build going there and I look forward to hearing how the ribbon burner works for you.

Unfortunately low pressure residential natural gas burner systems are a bit different than the relatively high pressure propane systems most gassers use. Not to burst your bubble or anything, but there are a couple of design issues that you may have:

Mixing pipe line losses: First for the 2" mixer piping you have, those lovely coped elbows will shed a whole bunch of static from your blower (whichever you end up using). Typically an elbow like that one is evaluated for blower selection in terms of equivalent length of straight piping. If your 2" line is going to be used to transfer say 100 CFM of air/gas mixture you can expect around 24 inches of water gauge (WG) pressure loss per 100 feet of ducting. This is not a problem, until you realize that those coped angles are the equivalent of around 30' of straight duct each. That means that without the ribbon burner's losses you still have around 17" WG (0.6 psi) of pressure to develop in the line for the system to overcome the losses of your pipe routing. Note that residential natural gas pressure is only around 7 - 14" WG, so that could be a problem also. Of course that changes depending on how much air gas mixture you are sending through the line.

Gas line size: I have a similarly sized forge with residential natural gas. I'm not sure exactly what my pressure is, as it runs a long way out to the forge via underground 1 1/2" gas line I installed (and I haven't put in a gauge yet), but the bottom line is that I have a 1" natural gas line feeding my forge, and when I tried a 1/2" line with a smaller mixer it wasn't sufficient. Perhaps your ribbon burner and build will be better than mine, but I'm afraid that depending on the length of run for your gas line that 1/4" will not be sufficient.

Preignition: with your burner on the top of your forge and made out of hard refractory it will get quite hot if the air source is turned off for any reason, please be careful to run air through the system before cracking open the gas if you take a break from forging. Also, if your mixture flow velocity isn't high enough due to the flow restrictions mentioned above, you might get the flame front getting backed up to the burner. One of the other advantages of the ribbon style burner is that the local velocity at each jet increases, so it helps prevent the backflash I'm concerned about, but keep an eye on things. If the burner begins to get really hot and you get a ignition inside your mixer you will likely trash your burner head or blower at the very least.

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You bring up lots of good points. One of the things I read about is the need to introduce the NG 9times the diameter of the pipe in inches from the burner due to NG not mixing as well as propane. (9x2"pipe= minimum 18" from the burner) ((the article mentions a longer introduction is even better)) What is your setup along these lines? Pictures would be great!

The cut and welded corners can be easily changed if this causes problems and I can see some turbulence being created naturally because of the sharp bends, but I'm hoping I'm adding to point one here.

My oil burner furnace for melting metal is also made from mizzou and gets wayyy hotter than natural gas burns at. So far I've suffered zero cracks in the material. It's still not too late at this point to relocate the burner to the side of the air tank. Here is a link to a guy on youtube with a ribbon burner mounted on the side. https://www.youtube.com/watch?v=jK5z6malbQ0

I'm really hoping on the design of the ribbon burner to prevent overheating of the metal body of the burner. With my oil burner, the tuyere is on the side and the oil nozzle is only a short 4inches up the pipe from the intense heat of the furnace. The side entry might be better......... Anyone else running a top entry? I find it hard to believe I'm the only one with a setup like this that hasn't run a build thread here. Hopefully more will chime in.

Thanks gang for the help so far and safety suggestions are appreciated, I don't need to end up in the newspaper. lmao

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The preignition I had concerns about is not a matter of cracks (which are more a issue with differential thermal expansion and overly short temperature cycling), but the potential for the flame front to reach inside your mixer, which is a bad idea for a premix type burner like the one you have built. Top or side mounting is probably not a big issue in such a small enclosure, the key is to keep air running thru the burner while the forge interior is hot.

I've used Mizzou as a castable refractory interior lining before and it works great. Doesn't always like short thermal cycling, but you can check with the manufacturer on their recommendations for heating and cooling. Not as flux resistant as some of the higher alumina castables, but certainly better than either insulating castable, soft brick, or frax blanket.

Here is my piping setup. Note that I use industrial burner parts that were originally part of a glass studio. Setup is still being massaged, I may remove one elbow from the airline to increase the air available, and the door system is quite rudimentary right now. The butterfly air valve, ventauri mixer and zero pressure regulator are really nice to use, but you can get by without them. Check Dudley Giberson and Henry Halem's books for some nice, simple burner designs.

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No ribbon burner yet. Have an old Giberson head that I may try out, if it isn't too badly cracked (high alumina refractory multi port head in a cylindrical configuration, mine is at least 15 years old). I'm currently using a SS flame retention nozzle that came with the burner assembly. If I go up to the Giberson I'll have to cut a larger hole.

Mizzou isn't that bad for flux (glass) contact, as long as it isn't swimming in it. I had some on the floor of a pleated frax glory hole (hot glass reheating equipment, don't get the wrong idea ) that I used every day for 12 years and didn't have a melt thru due to glass spalling off puntys. I'm pretty sure molten soda lime silica glass is just as corrosive as molten flux.

Floor in my current forge is lined with a thin layer of bubble alumina. You could also use a high alumina hard brick split (Cristalite) but they are pretty expensive (that is what I'm using for the shelf and temporary door outside my forge, but I had them laying around for the last 25 years, so why not).

I am familiar with Wayne's excellent resource. May build one of that style burner some day.

Industrial mixers are the ticket, if you can source one cheap, like I did. True ventauri inducers and zero pressure regulators for stable mixture proportion over a range of heat output. My old setup even had programmable PID control of temperature with UV sensor on a pilot and high/low fire control.

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I think what you are looking for is fairly rare in the blacksmith community. My setup is pretty unusual as far as I know. For some good info on "ribbon" burners (or burners with small multiple outlets for the burner head in whatever configuration) I urge you to look at the info on Dudley Giberson's site. He has been at it for quite a few years and knows his stuff as far as the premix with ribbon style burner head systems, and now even has a design specifically for small forges. That one uses propane and a ventauri, but his standard burner design works just fine for natural gas and a blower: http://www.joppaglass.com/burner/coup_mix.html. Note the inline configuration to get the most out of the low pressure squirrel cage blower. I believe that the turbulence and backpressure of the burner head works fine for getting the mixing required without the 9 pipe diameters you mentioned in the above.

Please be sure to click on the image for more detail on the burner orifice size and construction.

Note that I have no financial connection with Dudley, just know that he is a stand up guy with a great product. This page on his site is also of interest and give some info on the size burner head he recommends for a small forge: http://www.joppaglass.com/new_ideas/forge_page.html. Note in particular the ram-cast burner block he uses for the forge connection to the ribbon burner. I cast a similar one out of Mizzou for my glass furnace and it lasted for over 12 years of virtually constant use. This casting will help protect the burner head as well as the connection to the forge.

Again, these are his designs, and could have easily been found online with a simple search. My design is quite a bit different and influenced by my years of researching and building glass furnace burner assemblies.